This invention relates to a process for the production of 1, 5, 9- and 1, 6, 9-trimethylcyclododecatriene-(1, 5, 9) which are cyclic trimers of isoprene by a catalytic oligomerization of isoprene, and more particularly to a process for the production of isoprene cyclic trimers by employing a catalyst having improved characteristic features.
Heretofore, there have been a great number of patents and reports relating to studies on the production of each corresponding cyclic trimer by oligomerization of conjugated diene compounds with respect to butadiene, while relatively few reports on the study for such production of cyclic trimers with respect to isoprene are to be found.
Catalysts used for cyclic trimerization of isoprene may be classified broadly into the following three categories: A first group in which the Ti-based catalysts are employed has been proposed by the specifications of Japanese Patent Publication Nos. 2372/1960, 6170/1961, 17559/1962, 6468/1963, 14927/1963, 15375/1963, 29496/1970, 4456/1974, 4457/1974, 7154/1974, 7155/1974, 5933/1972, 7628/1973, 19303/1973, and 4215/1974, respectively. A second group in which Ni-based catalysts are adopted has been proposed by the specifications of Japanese Patent Publication Nos. 16882/1963, 14673/1964, 19156/1964, 22975/1968 and 31138/1975, Japanese Patent Laid-open Nos. 56950/1974, 56951/1974, 93941/1975, 68504/1976 and 98242/1976, respectively. A third group in which Cr-based catalysts are adopted has been proposed by the specifications of Japanese Patent Publication Nos. 5718/1961, 17559/1962, 6902/1974, 48307/1974 and 3054/1971, respectively.
In a process in which the Ni-based catalysts in the above-mentioned categories are employed, the catalyst concentration may be high, in general, and as a result, the yield based on the catalyst is low. There is also a great difference between the resultant cyclic trimers in their structures, i.e., a trans-trans-trans product is the principal component in the Ni-based catalysts, whilst a trans-trans-cis product is the principal product in the Ti-based catalysts. In a process in which the Cr-based catalysts are used, the catalyst concentration must be high similarly as in the case of the Ni-based catalysts, and as a result, the yield of trimethylcyclododecatriene based on the isoprene is low, i.e., less than 50%. Under the circumstances, when the process is carried out with a Ni- or Cr-based catalyst of a low concentration, its reaction velocity may be very slow, which requires much time for the process. The efficiency thereof may be inferior. These problems accompanying the use of these catalysts have been difficulties in industrial applications thereof. In the use of the Cr-based catalysts, a process for intensifying the catalytic activity by adding an aliphatic halo-compound has been proposed in Japanese Patent Publication No. 23377/1971. In this process, however, a by-product of a higher polymer which is adherent to a reaction vessel due to the aliphatic halo-compound may be produced easily.
On one hand, tetra-valent titanium compounds have been principally employed as Ti-based catalysts in conventional processes but have been accompanied by disadvantages such as the ease with which such tetra-valent titanium catalysts are poisoned by impurities such as moisture although these catalysts have high catalytic activities, and furthermore, a by-product of a higher polymer which is adherent to the reaction vessel is easily produced. Such a polymer which adheres to the reaction vessel is insoluble in a solvent and adheres to cooling coils and the like in the reaction vessel, thereby obstructing thermal conduction, and gives rise to troubles, so that it has been difficult to continuously carry out the reaction. In order to eliminate such difficulties as mentioned above, a process in which organoaluminum compounds are not used has been disclosed in the specification of Japanese Patent Publication No. 15375/1963. However, this process may be complicated because it requires pulverization with a ball mill at the time of a preparation of the catalyst.
In the above described three types of catalysts, the Ti-based ones can be considered to be advantageous because of their high activities. Accordingly, if the above described problem relating to the by-product of the polymer with adhesiveness to the reaction vessel, which has been frequently observed in the case where Ti-based catalysts are employed, can be solved, the above advantage afforded by the use of the Ti-based catalysts can be more favourably utilized.